I was just curious on behalf of those that don't trust wallet software and wanted to be hardcore about it.
In general, I would say that you probably are not going to be better off "manually" selecting your seed. Many who attempt to generate a seed outside of a computer program will adopt a procedure that is not truly random and will generate a seed that is vulnerable to theft.
Further, in order to spend your coin, you will need to use some software that is used to generate and sign a transaction.